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Re: MPLS TE/GB-TE tunnel traffic priority against normal traffic

  • From: Eric Osborne
  • Date: Tue Aug 21 00:04:16 2001

On Mon, Aug 20, 2001 at 02:52:23PM +0800, Yu Ning wrote:
> Hi nanog,
> When MPLS TE is partially deployed in an AS, in a given interface,
> there is coexistence between TE tunnel traffic, and normally per-hop
> routed traffic. Since the TE tunnel bandwidth was "booked" in
> advance via RSVP, I wonder if this part of TE bandwidth promise can
> be kept strictly by the router via build-in queuing mechanism when
> actually tunnel traffic comes in?

No; no implementations that I know of police a reservation like that.

> Or on the contrary, the bandwidth reservation is only an planning
> step, no actual priority queuing protection on them against normal
> traffic ?

Correct.  You still need to use regular diffserv to control traffic
priority/drop.  Part of the reason for this is that you can forward
multiple precedences down a single LSP, and all of those precedences
may require different treatment.

>  If normal MPLS-TE didn't handle my question, will Cisco's new
> GB-TE(two pools) handle it ?

Nope.  DS-TE (diffserv-aware TE) just gives you two pools.  We've been 
suggesting to use one pool for LLQ traffic, but that's only because
doing things that way seems to make sense.  You still need to
configure any physical packet treatment seperately.  This gives you
the flexibility to reserve a LLQ path from the DS-TE subpool, but send 
both in-rate and out-of-rate LLQ traffic down the LSP.

> Note, my question is different from the 8 preemption levels defined
> in MPLS-TE, the 8 preemption priority is used at the admission
> control phase, not when actual traffic comes in.

Agreed; tunnel preemption priority is a thing used between tunnels,
not for the traffic heading down tunnels.  Although a tunnel with a
better priority will tend to carry more important traffic.


> thanks for any input.
> Yu Ning
> ____________________________________________
> (Mr.) Yu Ning, Chief Engineer
> ChinaNET(AS4134) Sr. Sup.& New Sev. R&D
> Internet Product Dep. DCB, China Telecom
> Beijing, P.R.China +86-10-62072357/62072354
> ____________________________________________